Label for a mark sensing system

ABSTRACT

A coded retroreflective label for use in an automatic vehicle identification system. The label comprises a vertical array of rectangular orange, blue, white, and black retroreflective stripes arranged in selected paired combinations whereby to represent in a two-position base-four code format information pertaining to a vehicle on which the label is affixed. Distinguishable coded START and STOP stripe-pairs are provided at opposite ends of the array to respectively initiate and terminate processing of the data content of the label. Each white stripe paired with an orange or a blue stripe is masked with a plurality of black nonreflecting dots to reduce the reflectivity thereof to approximate that of the orange or blue stripe paired therewith. A black nonretroreflective border is also provided to isolate the stripes from the background on which the label is disposed.

United States Patent [72] inventors Francis H. Stites 8 Bennett Road, Wayland, Mass. 01778; Bradstreet J. Vachon, 32 Prior Drive,

Framingham, Mass. 01701 {21 App]. No. 745,585 [22] Filed July 17, 1968 [45] Patented Mar.9,1971

[54] LABEL FOR A MARK SENSING SYSTEM 4 Claims, 2 Drawing Figs.

{52] US. 235/61.12 Z51] Int. Cl G06k 19/00 [50] Field ofSearch ..235/6l.ll5,

61.12; 250/219, (lO,lDC); 340/1463 (RR); 350/105; 283/8 (R); 356/192, 191; 283/9 (R),

(lnquired) [56] References Cited UNITED STATES PATENTS 2,592,882 4/1952 Fisher'et a1. 350/105 3,211,470 10/1965 Wilson 235/61.l2

OTHER REFERENCES Barber, 21 Ways to Pick Data off Moving Objects, Control Engineering, October 1963, p. 82 & 83.

SCANNING olkecrloua Judd, Color in Business, Science & Industry, Wiley 8; Sons, 1952, p. 290- 296.

l-lausmann & Slack, Physics, Van Nostrand, 1935 p. 622

& 623.

Primary Examiner-Daryl W. Cook Assistant ExaminerThomas J Sloyan Attorneys-Norman J. OMalley and Elmer J. Nealon ABSTRACT: A coded retroreflective label for use in an automatic vehicle identification system. The label comprises a vertical array of rectangular orange, blue, white, and black retroreflective stripes arranged in selected paired combinations whereby to represent in a two-position base-four code format infonnation pertaining to a vehicle on which the label is affixed. Distinguishable coded START and STOP stripepairs are provided at opposite ends of the array to respectively 7 initiate and terminate processing of the data content of the label. Each white stripe paired with an orange or a blue stripe is masked with a plurality of black nonreflecting dots to reduce the reflectivity thereof to approximate that of the orange or blue stripe paired therewith. A black nonretroreflective border is also provided to isolate the stripes from the background on which the label is disposed.

ORANGE BLUE BLUE BLUE BLACK WHITE WHITE ORANGE.

BLUE WHITE BLACK BLUE ORANGE ORANGE BLACK ORANGE ORANGE WHITE WHITE WHITE WHITE BLUE PAIENIEDHAR em 3,669,676

BLOCK w SIGNAL SCANNING 'UNIT NORMALIZING WHEEL c ITR SENSOR 23 CIR U Y ON /OFF CONTROL FIG. 2

STOP ORANGE READ BLUE BLUE BLUE BLACK WHITE WHITE ORANGE BLUE WHITE BLACK BLUE ORANGE ORANGE BLACK ORANGE ORANGE WHITE WHITE WHITE WHITE BLUE BLUE ORANGE INVENIORS FRANCIS H. STITES BRADSTREET J. VACHON AITORNfV --SCANNING DIRECTION w u a U1 0 \1 0o 0 LABEL FOR A MARK SENSING SYSTEM CROSS-REFERENCE TO RELATED APPLICATION The present application is a divisional application of a copending patent application of Francis H. Stites and Bradstreet 3. Vachon, Ser. No. 386,328, filed Jul. 30, 1964, now Fat. No. 3,417,231, entitled MARK SENSING SYSTEM, and assigned to the same a'ssignee as the present application.

BACKGROUND OF THE INVENTION The present invention relates to a reflective label, and more particularly, to a coded retroreflective label for use in a mark sensing system for identifying railroad cars.

In the railroad industry, freight cars are transported throughout the North American continent and a particular car may be away from the home railroad for months or even years at a time. To keep account of these cars, each railroad must maintain elaborate records of the location, routing, and identifying numbers of their cars and must'exchange-accounts with other railroads. Initial recording of the cars is generally accomplished by the laborius and inaccurate means of manually listing the car number, the railroad name and other pertinent information for each car in a train consist before the train leaves the yard. In some instances, closed circuit television has been employed wherein an operator in a control booth of a switch yard notes the identity of cars passing a television camera located in th'e yard. Although this method offers some improvement over the manual method, this system still depends on a human operator and is subject to the attendant clerical errors. In addition, the operability of this system is limited in poor weather conditions such as rain, snow, or fog.

Various automated means for identifying railroad cars have been suggested from time to time; however, these means have failed to satisfy the requirements of a commercially acceptable system by reason of cost, complexity, or poor operation under practical environmental conditions. Previously suggested techniques for car identification have employed electromagnetic, radioactive, sound, or optical sensing of appropriately-coded indicia. In a known magnetic system, a bar of magnetizable material having coded notches therein is fastened to the undercarriage of a car where it is sensed by a transducer located between the tracks. This scheme suffers major disadvantages, one being the cost of the coded bar and the cost and time expended in securing the bar to the car, usually by welding. Furthermore, the transducer must be within a few inches of the coded bar to obtain proper opera tion, which necessitates placing the bar close to the ground, such as under the track, where it is subject to extreme vibration. Moreover, as the car can sway several inches laterally, the bar may not be in a position to be sensed by the transducer.

Another known system employs a series of precisely tuned piezoelectric crystals mounted beneath a car a few inches from the ties wherein the transducing apparatus is located. Each crystal responds to an interrogating signal with a particularly tuned return signal which represents a coded digit. The car is identified by interrogating the crystals with a signal transmitted from the transducing apparatus and noting the frequencies of the signals returned by the crystals. Although academically this system operates as intended, its commercial potential is seriously limited by certain deleterious features.

First of all, the crystal designator is relatively expensive and extremely delicate, thus making it impractical for use on hundreds or thousands of railroad cars. In-addition, the designator must be mounted beneath the car, which can not easily be done without taking the car out of service and installing the designator in a service shop. Furthermore, complex receiving circuitry is necessary to decode the signals returned by the crystals since these signals are at a plurality of closely-spaced frequencies. Thus, this technique does not lend itself to an easily installable, trouble-free and relatively inexpensive system.

Several optical systems have been evolved which generally employ a coded label located on the side of the railroad car which is optically scanned by apparatus located at trackside. In optical systems heretofore proposed, the labels have been coded by either black and white stripes which indicate the presence or absence of a numeral in an appropriate code, or by colored stripes wherein the information is represented by suitable color combinations. In some of these systems, the particular code utilized requires an extremely large label, 3 to 4 feet in length, in order to represent the requisite information, which, of course, increases the cost of the label and makes it unwieldy to apply to a car. These known systems have not been-extensively tested in the field and even those tested in a laboratory have not proven to be sufficiently accurate or relia-' ble to be commercially attractive.

A label reading systemwherein most of the deficiencies of the prior art were overcome has been previously disclosed'in a copending application Ser. No. 137,918, of Francis H. Stites and Raymond Alexander, filed Sept. I3, 1961, now US. Pat. No. 3,225,177, and -a'ssigned to the assignee of the present application. This previous system employs optical scanning of a retroreflective label. The present invention relates to a retroreflective label similar to that employed in the above mentioned optical label reading system, however, incorporating certain features developed as a result of judicious study of operating problems encountered in practice.

It is, therefore, a primary object of the present invention to provide an improved label; 7

In accordance with the present invention, a label is provided for a mark sensing system. The label which comprises stripes of orange, blue, black and whiteretroreflective material arranged in accordance with a two-position base-four code, by various two-stripe combinations of the orange, blue, white and black stripes to represent start and stop signals and'alphanumeric figures. The various stripes are mountedhorizontallyin' a vertical array on the side of a vehicle. As is well known, retroreflective material reflects substantially all the light impinging upon it back along the path of incidencerEach of the white stripes of the above-described label and, in particular, each of the white retroreflective stripes paired with an orange retroreflective stripe or a blue retroreflective stripe, is partially masked by a plurality of black, nonreflecting elements such as spots. These black, nonreflecting elements serve to reduce the reflectivity of the white stripes, which is greater than the reflectivity of orange stripes or blue stripes, and are provided on each white stripe in sufficient number so as to reduce or attenuate the reflectivity of the white stripe to approximate the reflectivity of an orange stripe or blue stripepaired therewith. By employing black nonreflecing element on the white stripes as described above, a pulse produced in response to scanning a stripe-pair including a white stripe does not have two peaks, one corresponding to the white stripe and the other corresponding to the orangeor blue stripe paired therewith, with the peak corresponding to the white stripe being of greater amplitude. By insuring that a pulse derived from a two-stripe combination including a white stripe has-an approximately uniform amplitude, the possibility of error occurring in the measurement of the width of such pulse during subsequent processing and the possibility of misreading a digit encoded by a stripe-pair including a white stripe, which might otherwise occur for a double peak pulse, is lessened. To read the above-described coded label, a trackside optical reading unit vertically scans a beam of light across the coded label. The light retroreflected from the label is directed back to the reading unit where it is translated into coded information representative of the data encoded in the label. A particularly suitable trackside reading unit which may be used in'r'eading the above-described label is described in the above-mentionedapplied to respective sensors, the output signals of which are suitably processed to provide the requisite decoded information. The signals appearing at the output of the sensors are coded pulses representative of the particular label figures read by the scanner.

BRIEF DESCRIPTION OF THE DRAWING GENERAL DESCRIPTION Referring to FIG. ll, there is shown a mark sensing system, described in detail in the aforementioned patent to Stites and Vachon, with which a coded label 12 in accordance with the present invention may be employed. A light beam from a trackside unit is caused to repetitively vertically scan the label 112, the label 12 being affixed to the side of a railroad car 14. Light reflected from the label is received by the scanning unit 10 and is transduced into electrical signals which are applied to normalizing circuitry 16 which removes essentially all distortion and provides standardized pulses representative of the coded label information. The standardized pulses are decoded by decoding logic circuitry 18 the output signal of which operates a readout apparatus 20, such as a teletypewriter printer. The decoding logic circuitry 18 preferably includes an acceptance gating arrangement 18' which causes the decoding logic circuitry 18, also described in detail in the aforementioned patent to Stites and Vachon, to apply output signals to the readout apparatus 20 only when the signals derived from the scanning operation have been determined to be those derived from the label 12 only.

The above-described system is in a deenergized condition until a train enters the signal block within which the scanner is located. At this time a command from a block signal 22, which is a standard item of railroad signalling equipment, actuates the trackside scanning unit 10 and the associated electronics via an ON/OFF control 21. A wheel sensor 23 and wheel counter logic 24 are employed to provide information to the decoding logic circuitry 18 and the readout apparatus 20 concerning unlabeled or unreadable cars.

A detailed description of the label 12 in accordance with the invention will now be presented.

LABEL The label 12, shown in FIG. 2, is fabricated from pressuresensitive adhesive-backed retroreflective material, such as that sold commercially under the trademark SCOTCI-ILITE" by the Minnesota Mining and Manufacturing Company. Information identifying the car is coded by two-stripe combinations of orange, blue, white and black stripes arranged in a vertical succession of horizontally-disposed stripes. Each bit of information is represented by two stripes in various combinations of these colors; thus, a two-position base-four code results. This code achieves a considerable saving in label size over the more common binary type code. As seen in FIG. 2, the label 112 includes, from bottom to top, a Start Read code, encoded decimal numbers one through zero, and a Stop Read code, and is scanned vertically from bottom to top by the scanning apparatus. In addition, a wide white stripe 25 is provided on the bottom of the label before the Start Read" code, the function of is to clear the decoding logic circuitry 18 (FIG. I) of spurious information which may be present before the reading cycle starts.

The orange and blue stripes of the label 112 reflect light in the orange and blue spectrum, respectively, while the white stripes reflect light in both the orange and blue spectrum. The black stripes do not reflect significantly; however, the absence of reflected light is utilized in the label code along with the orange, blue, and white light returns, to effectively provide four colors. The black stripe is utilized in the label code only for the second stripe of the two-stripe combination since system timing pulses areinitiated in the decoding logic circuitry 8 (FIG. 11) by the light reflected from the first stripe in every two-stripe combination. It will be noted that the Start Read and Stop Read code utilize blue and orange stripes, while data is represented by blue or orange stripes in combination with white or black.

As briefly stated previously, and as described in detail in the aforementioned patent to Stites and Vachon, the trackside unit It) includes an orange sensor and a blue sensor. In operation, the orange sensor responds to light reflected from the orange stripes, the blue sensor responds to light in the blue spectrum, and both sensors respond to light reflected from the white stripes. Neither sensor responds as a result of scanning a black stripe. Thus, particular bits of information are distinquished by the corresponding coded signals produced by the sensors.

The amplitude of the light reflected from the white stripes is greater than that reflected from the orange or blue stripes, causing the signals produced by the sensors in response to white light to be of correspondingly greater amplitude. As stated previously, in order to equalize the amplitude of sensor signals for colored and white light, an attenuator is provided for the white stripes in the form of a sufficient number of black dots superimposed over the white stripes to reduce the reflectivity of these stripes to essentially equal that of the colored stripes. In the above fashion, a pulse produced in response to scanning a stripe-pair including a white stripe does not have two peaks of unequal amplitude and the possibility of error occurring in the measurement of the width of such pulse or the misreading of a digit encoded by a stripe-pair including a white stripe is lessened.

In a system which has operated satisfactorily, the stripes are each 6 inches long and three-eighths inch wide, and the spacing between paired stripes is one-half inch. The coded stripes are surrounded by a black, nonreflective border, and each coded digit or instruction is separated from adjacent ones by a nonreflective stripe. This prevents unwanted reflections from the surface of a railroad car, especially stainless steel or aluminum cars, which may cause spurious signals which could falsely trigger the processing circuitry. The Start Read" and Stop Read stripes are each 4 inches long and overlap each other by 2 inches as shown st so that reading is not initiated until approximately 2 inches of the label is in view of the scanner, since a reflection from both stripes is required to enable the decoding logic circuitry 18. Thus, only the central portion of the vertical array of stripes is read." Consequently, if the vertical edges of the label are tattered or otherwise deteriorated, the scanned information is not affected since reading does not begin until both stripes of the Start Read" code are scanned.

It is important to maintain uniform the relative brightness of the stripes comprising a coded digit. This is accomplished by fabricating each coded digit from a common piece of white retroreflective material and then silk screening the color on as needed. In this manner, variations in brightness caused by variations in different base material are eliminated. Variations in brightness between consecutive numbers is not critical.

We claim:

I. A label for use in a mark sensing system including: an array of parallel stripes including reflective stripes of a first color, a second color, and a third color, the stripes of the third color having a greater reflectivity than stripes of the first color or stripes of the second color, said stripes being arranged in selected paired combinations, each of the stripes of the third color paired with a stripe of the first color or a stripe of the second color being partially masked with a plurality of nonreflective elements to reduce the reflectivity of the stripe of the third color to approximate that of the stripe of the first color or second color paired therewith; an additional first pair of reflective stripes at one end of said array for initiating processing of the data content of the label, said additional first pair being distinguishable from the other pairs of stripes; and an additional second pair of reflective stripes at the other end of said array for terminating processing of the data content of the label, said additional second pair being distinguishable from the other pairs of stripes. Y

2. For use in a mark sensing system, a label comprising, a vertical array of parallel horizontally-disposed retroreflective stripes of equal vertical width and equal horizontal length, said stripes being of four different colors and arranged in paired combinations in a two-position base-four code to define alphanumeric data, predetermined ones of said stripes of four different colors having a greater reflectivity than predetermined other ones of said stripes of four different colors, each of said predetermined ones of said stripes of four difi'erent colors being partially masked with a plurality of nonreflective elements to reduce the reflectivity thereof to approximate that of the predetermined other ones of said stripes of four different colors, each two-stripe combination by a nonreflective spacer, an additional first pair of retroreflective stripes at one end .of a said array of stripes for initiating processing of the data content of the label, the stripes of said additional for first pair being of equal horizonatal length and shorter than the stripes of the array, the stripes of the additional first pair extending inwardly from opposite edges of the label and contiguous with each other at a central portion of the label, and an additional second pair of retroreflective stripes at the other end of said array of stripes for terminating processing of the data content of the label, the stripes of said additional second pair being of equal horizontal length and shorter than the stripes of the array, the stripes of the additional second pair extending inwardly from opposite edges of the label and contiguous with each other at the central portion of said label.

3. For use in a mark sensing system, a label comprising, a vertical array of parallel horizontally-disposed retroreflective stripes of equal vertical with and equal horizontal length, said stripes being arranged in selected paired combinations of orange, blue, white and black stripes to provide a twoposition base-four code, said white stripes being partially masked with black nonreflective dots to reduce the reflectivity of the white stripes to approximate that of the orange and blue stripes, an additional first pair of retroreflective stripes at one end of said array of stripes for initiating processing of the data content of the label, the stripes of said additional first pair being orange and blue and of equal horizontal length, the stripes of said additional first pair being shorter than the stripes of the array and extending inwardly from opposite edges of said label to a point beyond the center of saidlabel so as to be contiguous in the central portion of the label, an additional second pair of retroreflective stripes at the other end of said label for terminating processing of the data content of the label, the stripes of said additional seocnd pair being blue and orange and shorter than the stripes of the array, the stripes'of the additional second pair extending inwardly from opposite edges of said label to a point beyond the center of said label so as to be contiguous in the central portion of the label, and a white retroreflective element for clearing the mark sensing system to allow the content of the label to be processed, said white retroreflective element having a vertical width greater than the vertical width of the stripes of the label and disposed adjacent said additional first pair of stripes.

4. For usein a mark sensing system, a label comprising, a vertical array of parallel horizontally-disposed retroreflective stripes of equal vertical width and equal horizontal length, said stripes being arranged in selected paired combinations of orange, blue, white and black stripes to providea two-position base-four code, said white stripes being partially masked by black dotsarran ed thereon in a checkered pattern to reduce the reflectivity o the white stripes to approximate that of the orange and blue stripes, each paired combination of stripes being separated from the adjacent paired combination by a black nonreflective spacer having a vertical width approxi-.

mately equal to the vertical width of the stripes, said stripes being bounded on their vertical edges by a black nonreflective border for isolating the stripes of the label from the background on which the label is disposed, an additional first pair of retroreflective stripes disposed at one end of said array for. initiating the processing of the data content of the label, the stripes of said additional first pair being orange and blue and of equal horizontal length, the stripes of said additional first pair being shorter than the stripes of the array and extendinginwardly from opposite vertical edges of said label to a point beyond the center of said label so as to contiguously overlap in the central portion of the label, an additional second pair of retroreflective stripes disposed at the other end of said array for terminating processing of the data content of the label, the stripes of said additional second pair being blue and orange and shorter than the stripes of the array, the stripes of the additional second pair extending inwardly from opposite vertical edges of the label to a point beyond the center of said label so as to contiguously overlap in the central portion of the label, and a wide white retroreflective element having a greater vertical width than the stripes of the label disposed adjacent said additional first pair of stripes, said wide stripe being adapted for clearing the mark-sensing system to allow the content of the label to be processed.

age UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 5 626 Dated r-M1 q l Q71 Inventofls) Franc-i n stiteq and Bradstreet J, Vachon It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading of the-patent, below the line [45] Patented Mar. 9, 1971', insert [73] Assignee Sylvania Electric Products Inc.

a corporation of Delaware Division of application Ser. No. 386,328, Jul. 30, 1964, now Pat. No. 3,417, 231-- Column 1, line 22, change "laborius" to--laborious- Column 2, line 49, change "nonreflecing element" to --nonreflecting elements-- Column 3, line 36, after "18' insert--, also descri bed in detail in the aforementioned patent to Stites and Vach0n,-; lines 37 and 38, delete also described in detail in the aforementioned patent to Stites and Vachon, line 73, after "of and before "is", insert--which-- Colnmn 4, line 50, delete "st":

In claim 2, column 5, line 24, after "combination", insert--being separated from the adjacent two-stripe combination--; line 26, delete "a"; line 27, delete "for" In claim 3, column 5, line 41, change "with" to -width--; column 6, line 6, change "seocnd" to--second- L Signed and sealed this 7th day of September 1971 (SEAL) Attest:

ROBERT GOTTSCHALK 1 M.FLETCHER JR. EDWARD Acting Commissioner of Pa Attesting f 

1. A label for use in a mark sensing system including: an array of parallel stripes including reflective stripes of a first color, a second color, and a third color, the stripes of the third color having a greater reflectivity than stripes of the first color or stripes of the second color, said stripes being arranged in selected paired combinations, each of the stripes of the third color paired with a stripe of the first color or a stripe of the second color being partially masked with a plurality of nonreflective elements to reduce the reflectivity of the stripe of the third color to approximate that of the stripe of the first color or second color paired therewith; an additional first pair of reflective stripes at one end of said array for initiating processing of the data content of the label, said additional first pair being distinguishable from the other pairs of stripes; and an additional second pair of reflective stripes at the other end of said array for terminating processing of the data content of the label, said additional second pair being distinguishable from the other pairs of stripes.
 2. For use in a mark sensing system, a label comprising, a vertical array of parallel horizontally-disposed retroreflective stripes of equal vertical width and equal horizontal length, said stripes being of four different colors and arranged in paired combinations in a two-position base-four code to define alphanumeric data, predetermined ones of said stripes of four different colors having a greater reflectivity than predetermined other ones of said stripes of four different colors, each of said predetermined ones of said stripes of four different colors being partially masked with a plurality of nonreflective elements to reduce the reflectivity thereof to approximate that of the predetermined other oneS of said stripes of four different colors, each two-stripe combination by a nonreflective spacer, an additional first pair of retroreflective stripes at one end of a said array of stripes for initiating processing of the data content of the label, the stripes of said additional for first pair being of equal horizonatal length and shorter than the stripes of the array, the stripes of the additional first pair extending inwardly from opposite edges of the label and contiguous with each other at a central portion of the label, and an additional second pair of retroreflective stripes at the other end of said array of stripes for terminating processing of the data content of the label, the stripes of said additional second pair being of equal horizontal length and shorter than the stripes of the array, the stripes of the additional second pair extending inwardly from opposite edges of the label and contiguous with each other at the central portion of said label.
 3. For use in a mark sensing system, a label comprising, a vertical array of parallel horizontally-disposed retroreflective stripes of equal vertical with and equal horizontal length, said stripes being arranged in selected paired combinations of orange, blue, white and black stripes to provide a two-position base-four code, said white stripes being partially masked with black nonreflective dots to reduce the reflectivity of the white stripes to approximate that of the orange and blue stripes, an additional first pair of retroreflective stripes at one end of said array of stripes for initiating processing of the data content of the label, the stripes of said additional first pair being orange and blue and of equal horizontal length, the stripes of said additional first pair being shorter than the stripes of the array and extending inwardly from opposite edges of said label to a point beyond the center of said label so as to be contiguous in the central portion of the label, an additional second pair of retroreflective stripes at the other end of said label for terminating processing of the data content of the label, the stripes of said additional seocnd pair being blue and orange and shorter than the stripes of the array, the stripes of the additional second pair extending inwardly from opposite edges of said label to a point beyond the center of said label so as to be contiguous in the central portion of the label, and a white retroreflective element for clearing the mark sensing system to allow the content of the label to be processed, said white retroreflective element having a vertical width greater than the vertical width of the stripes of the label and disposed adjacent said additional first pair of stripes.
 4. For use in a mark sensing system, a label comprising, a vertical array of parallel horizontally-disposed retroreflective stripes of equal vertical width and equal horizontal length, said stripes being arranged in selected paired combinations of orange, blue, white and black stripes to provide a two-position base-four code, said white stripes being partially masked by black dots arranged thereon in a checkered pattern to reduce the reflectivity of the white stripes to approximate that of the orange and blue stripes, each paired combination of stripes being separated from the adjacent paired combination by a black nonreflective spacer having a vertical width approximately equal to the vertical width of the stripes, said stripes being bounded on their vertical edges by a black nonreflective border for isolating the stripes of the label from the background on which the label is disposed, an additional first pair of retroreflective stripes disposed at one end of said array for initiating the processing of the data content of the label, the stripes of said additional first pair being orange and blue and of equal horizontal length, the stripes of said additional first pair being shorter than the stripes of the array and extending inwardly from opposite vertical edges of said label to a point beyond the cenTer of said label so as to contiguously overlap in the central portion of the label, an additional second pair of retroreflective stripes disposed at the other end of said array for terminating processing of the data content of the label, the stripes of said additional second pair being blue and orange and shorter than the stripes of the array, the stripes of the additional second pair extending inwardly from opposite vertical edges of the label to a point beyond the center of said label so as to contiguously overlap in the central portion of the label, and a wide white retroreflective element having a greater vertical width than the stripes of the label disposed adjacent said additional first pair of stripes, said wide stripe being adapted for clearing the mark-sensing system to allow the content of the label to be processed. 